For surface plasmon resonance (SPR) measurement, using a grating-type or a prism-type SPR inspection system, the measurement for the SPR angle is a key step. If the angle can be correctly adjusted and the detected signal can be analyzed, high-precision measurement can be achieved. To inspect multiple objects under test by adaptively adjusting the grating pitch, detecting resonance angle variation due to the thickness of the gold film and functional groups, it is required that the system has to be capable of adjusting the SPR angle corresponding to different objects under test.
Conventionally, a major company of SPR instrument, Biacore, discloses in U.S. Pat. No. 7,262,866 that an angle rotating mechanism is used to adjust the angles of the optical reflectors SM1 and SM2 so that the incident light beam reaches the surface of the prism or the grating to inspect SPR.
Moreover, in U.S. Pat. No. 5,341,215, a method and apparatus for detecting the presence and/or concentration of biomolecules by providing a boundary surface between an optically denser medium and an optically rarer medium. The angle of incidence is controlled by rotating a desk such that the intensity of the reflected light is always maintained at a minimum which ensures that the angle of incidence is equal to the angle at which SPR occurs.
Moreover, U.S. Pat. No. 7,265,844 discloses a mechanical linkage (10, 11) of planar mirrors 12 and 13 provides a single point adjustment of angle of incidence and angle of refraction while maintaining a constant optical axis of the light source and detector, as shown in FIG. 1A and FIG. 1B, to achieve optical inspection when an incident angle is equal to the reflected angle.